1959 Onderstepoort Journal of Veterinary Research, Volume 28, Number 1 & 2, 1959
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Item Sweating sickness : the present state of our knowledge(Pretoria : The Government Printer, 1959) Neitz, W.O.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.This is an informative review of all aspects of the tick-borne toxicosis known as 'sweating sickness'. The condition principally affects young calves although sheep, pigs and goats are also susceptible. It occurs in Central, Eastern and South Africa, southern India and Ceylon and this review would be of particular interest to veterinarians in those parts of the world. The author, who considers that the causal agent is a toxin, discusses the history, aetiology, transmission, epizootiology, pathology, symptoms, diagnosis, treatment, prophylaxis and immunity of the disease. A very useful list of references is appended and the text is interspersed with fourteen detailed tables dealing with experimental data, distribution and hosts of tick vectors.Item Tick paralysis in the Karoo areas of South Africa(Pretoria : The Government Printer, 1959) Stampa, S.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.1. Four forms of tick paralysis in South Africa may be distinguished, which differ as regards the clinical picture and are associated with four distinct tick species. 2. The literature dealing with tick paralysis in South Africa is briefly reviewed. 3. The seasonal occurrence of the adults, nymphae and larvae of I. rubicundus is given. 4. The adult is both nocturnal and diurnal and it is possible to demonstrate a peak in diurnal activity between 10 a.m. and 2 p.m. 5. The immature stages are exclusively nocturnal. 6. The influence of temperature upon larval activity is demonstrated graphically. 7. A host list is given which shows that the Menotyphla and Lagomorpha play the main role as hosts of the immature stages. The Artiodactyla constitute the main hosts of the adult tick amongst the wild animals. The tick is not found on birds. 8. The attachment sites of the adult stages on adult sheep and lambs are given and the chances of reaching full engorgement on the different regions of the body of the sheep arc discussed. The preferential sites for I. rubicundus and I. ricinus are compared and the differences in habit of these two species on sheep described. 9. The time required by the female to reach full engorgement in different situations on the bodies of sheep is given. 10. The stages of engorgement normally observed are described and exceptions to this rule are discussed. 11. The percentage of females that fail to reach full engorgement on sheep is shown to increase with the time the sheep spends in tick-infested veld. 12. The influence of copulation upon the rate of engorgement is discussed. 13. The use of tethered sheep in tick-infested veld as a means of tick survey is discussed. 14. An improvement on the standard technique of dragging for ticks, for use in the Karoo shrub, is described. 15. The attraction of different materials to I. rubicundus tested by the dragging technique in the field has been investigated. 16. Seven species of ticks found during the course of dragging are noted. 17. The uniformity of distribution of I. rubicundus larvae in the field is discussed. 18. The factors responsible for the losses of ticks from the apparatus during the course of dragging are demonstrated graphically and discussed. 19. A map showing the distribution of I. rubicundus and the occurrence of tick paralysis in relation to veld (pasture) types in a selected area in the Sneeuberg Range is included. 20. The ecological investigations of overseas workers on other tick species are reviewed briefly for comparison with the findings relating to I. rubicundus in South Africa. 21. An association between tick incidence and deterioration of pasture in the case of I. rubicundus is found to follow a pattern similar to that of I. ricinus in Britain. 22. The hatching and survival of the larvae of I. rubicundus are shown to represent phases of the life-cycle more susceptible to unsuitable environment than any other stage. 23. Experimental studies on the hatching and survival of eggs placed in decaying plant material under certain shrubs and rank grasses are described and compared with the differences observed when grasses are not allowed to become rank. 24. Significant differences in tick densities are shown to occur in different naturally-infested veld types. Sweet-grass mountain veld, constituting the original coverage of all mountains in the area under investigation, is not suited to the completion of the life-cycle of the tick. 25. The role played by Rhus erosa in the creation of suitable environmental conditions for the tick is pointed out. 26. The time required for bringing about an alteration in the existing plant associations by applying different methods of pasture management is discussed. 27. The influence of the regular dipping of sheep upon the incidence of I. rubicundus is demonstrated. 28. The exclusion of sheep from tick-infested camps during the active season of I. rubicundus is shown to have no effect upon the incidence of the tick. 29. The influence of veld fires upon the tick is pointed out. 30. The recommendations of other investigators for the control of I. rubicundus by dipping are compared with the application of dipping to the control of I. ricinus. 31. The specific efficacy of insecticides against the tick as found by a laboratory method, the ability of the insecticide to diffuse along the wool fibres and the quantity of insecticide deposited in the fleece rather than the concentration of the wash in the dipping tank, are shown to be the decisive factors governing the period of protection obtained against I. rubicundus. 32. BHC is shown to be capable of protecting woolled sheep against I. rubicundus for a period exceeding 18 weeks when 4·75 gm. of the gamma isomer is deposited per sheep. 33. Dieldrin is shown to protect woolled sheep for approximately 11 weeks when 7 gm. of the active ingredient is deposited per sheep. 34. The protection of sheep against Rhipicephalus evertsi and Hyalomma spp. by BHC has been tested. 35. The experience gained in the application of the foot- or walk-through bath for sheep is given.Item Ticks in the South African Zoological Survey Collection - Part IX - The Amblyomma marmoreum group(Pretoria : The Government Printer, 1959) Theiler, Gertrud; Salisbury, Lois E.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.*1. Amblyomma variegatum var. nocens, Robinson 1911, is re-established as a valid species with the new name combination of Amblyomma nocens.* 2. A list of synonyms is given for A. nocens and A. pomposum. 3. A. pomposum is shown to be distributed in the Rhodesian Highland type of vegetation; *A. nocens, according to present records appears to be confined approximately between latitudes 18 - 22° S. and between the Drakensberg and the coast.Item Culicoides gulbenkiani, a new species of Culicoides (Diptera Ceratopogonidae) in South Africa(Pretoria : The Government Printer, 1959) Caeiro, V.M.P.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.The description of Culicoides gulbenkiani is based on 15 females captured in a light trap, at Onderstepoort, within forty-two days (from 20th March, 1958 to 30th April, 1958); and on three females and one male from the Onderstepoort Laboratory collection identified by De Meillon in April 1956 as Culicoides milnei Austen. The careful study of these specimens show them to be a new species and not a variation of milnei. Unfortunately amongst the thousands of Culicoides captured in light traps daily no other males of this species were found.Item Ticks in the South African Zoological Survey Collection - Part XI - Ornithodoros eboris n. sp.(Pretoria : The Government Printer, 1959) Theiler, Gertrud; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.Ornithodoros eboris n. sp. male, female, nymph and larva are described for the first time. It belongs to the group of O. lahorensis, O. foleyi and O. delanoei with "madreporian"-like sculpturing.Item The technique of adrenalectomy in the sheep(Pretoria : The Government Printer, 1959) Hofmeyr, C.F.B.; Fitzpatrick, R.J.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.A technique for removal of the adrenal glands in the sheep is described; the difficulties associated with the anatomy of the right adrenal gland are emphasised.Item The histology of the cytopathogenic changes produced in monolayer epithelial cultures by viruses associated with lumpy skin disease(Pretoria : The Government Printer, 1959) De Lange, M.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.A study is reported of the cytological changes induced in cultures of calf and lamb kidney cells and lamb testis cells by three distinct groups of viruses associated with Lumpy Skin Disease. On the basis of the morphological changes produced one is justified in concluding that these viruses are entirely unrelated. The cytopathogenesis of a virus isolated from bovine faeces is also described. Attention is directed to the similarity of cytopathogenic effects of these viruses to those induced by other viruses causing known disease conditions. The value of the histological study of cytopathogenesis in relation to virus research is discussed.Item The histopathology of Wesselsbron disease in sheep(Pretoria : The Government Printer, 1959) Le Roux, J.M.W.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.1. The histopathology of Wesselsbron disease is described. The lesions are mainly confined to the liver. This organ shows fatty infiltration, bile pigmentation, necrobiosis of the liver cells and infiltration of lymphocytes and neutrophils. The histological picture tends to be variable and the lesions in experimentally infected cases are of a much milder degree compared to those observed in natural cases. 2. Immunisation of pregnant ewes produces meningo-encephalitis in the foetuses. 3. The differential diagnosis is discussed and it is suggested that enzootic icterus probably played a role during the 1957 outbreak of Wesselsbron disease.Item A study of the plasma sodium and potassium levels in normal Merino sheep(Pretoria : The Government Printer, 1959) Clark, R.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.(1) The following figures were deduced from determinations made on 500 samples of plasma from apparently normal Merino sheep. Plasma Sodium: Extreme range 132-- 156 m. eq./litre, mode 144, arithmetic average 144·11, 90 per cent of samples between 138 and 150. Distribution normal. Plasma Potassium: Extreme range 3·8- 6·0 m. eq./litre, mode 4·8, arithmetic average 4·804, 90 per cent of samples between 4·1 and 5-5. Distribution lognormal. (2) No differences could be found due to sex, season, salt dosing (on a basic diet of lucerne hay) or starvation for 96 hours. (3) The administration of A.C.T.H. caused retention of sodium and potassium but had no effect on the plasma levels due to concomitant water retention.Item Some factors affecting the secretion of abomasal juice in young dairy calves(Pretoria : The Government Printer, 1959) Grosskopf, Johannes Friedrich Wagner; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.Methods are described for the collection of abomasal secretion samples from calves and for the examination of the juice for proteolytic and rennin activity. The effect of the rennin and pepsin concentration of the secretion was studied during two different methods of feeding milk viz. nipple feeding and drinking from the open bucket. It was found that both ways of feeding caused an increase in the rennin and pepsin concentration of the juice but that the effect of nipple feeding was greater. The administration of carbamylcholine stimulated the abomasal secretion rate and also caused an increase in the rennin and pepsin content of the juice. The injection of atropine, on the other hand, inhibited these functions. It was also found that during a period of seven weeks the rennin concentration as well as the pH of the abomasal secretion of one calf fell steadily with increasing age.Item Ticks in the South African Zoological Survey Collection - Part X - Rhipicephalus mühlensi(Pretoria : The Government Printer, 1959) Salisbury, Lois E.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.1. The male and female of R. mühlensi are redescribed and the larva and nymph described for the first time, from material reared at Onderstepoort. 2. Host lists and geographical distribution for R. mühlensi and the closely related R. masseyi are given.Item A laboratory scale apparatus for the continuous culture of micro-organisms with automatic pH control(Pretoria : The Government Printer, 1959) Serfontein, W.J.; Weyland, H.; Alexander, R.A.; Clark, R.; Louw, J.G.; De Kock, V.E.The authors give technical details of their modification of the "chemostat" for the continuous culture of micro-organisms. Apparatus incorporates an automatic pH control and has given satisfactory results for runs lasting several weeks.